Field of the Invention
The invention relates to safety devices carried by injection valves of internal combustion engines.
Discussion of Background
The "pressure-time" injection principle is known which is characterized by the use of injection valves, fed under a normally constant pressure, delivering an amount of fuel in proportion to their opening time. Injection valves of this type have the drawback that, in case of jamming of the needle, breaking of the injection nozzle or failure of the control system, it is no longer possible to regulate the amount of fuel injected, it then being possible for the engine to suffer heavy damage.
A known device of this type is described in French patent No. 1 555 369. Such consists of a device placed in the intake line of the injection valve and/or in the exhaust line of the control valve or valves which are operated electromagnetically, which blocks one or the other of the lines described above, in case the maximum admissible amount of injected fuel is exceeded.
This device consists mainly of a piston moving in a bore. This piston is held on one side by a spring and, a line comprising a restriction is arranged parallel to the piston bore, this line coming out in the bore on the spring side. The piston face opposite the spring is connected to the fuel inlet and to the other end of the line mentioned above. The piston face, on the spring side, is connected to the injection valve. When injection occurs, the pressure is lowered on the face of the piston making it move by compressing the spring and, at the end of the injection the piston is returned by the spring. In case the injection valve is defective, the piston undergoes movement so that it comes to block the line described above, thus interrupting the flow. The restriction provided in the line is provided so that the piston can be returned to its original position under the action of the spring between two successive injections, even at very high engine speed.